Romans 6:19 : I speak after the manner of men because of the infirmity of your flesh: for as ye presented your members as servants to uncleanness and to iniquity unto iniquity, even so now present your members as servants to righteousness unto sanctification. Because they were slow to comprehend spiritual relations, he uses the customs of men as an illustration to enable them to see that, though they were not under law, but under grace, they had no more liberty to continue to serve sin than a man had to continue to serve one master after he had been transferred to another. Formerly they had presented their members as servants to uncleanness and to iniquity. Uncleanness has reference to the degrading immoral practices so common among sinners, such as lewdness, drunkenness, etc. The word from which we have "iniquity" means lawlessness, and has reference to their former attitude toward God. They did not regard his law. As they formerly lived an unclean and lawless life, they are now to present their members as servants to righteousness unto sanctification. Formerly their members had been used in worldly living; now they are to separate them from such worldly uses and dedicate them to the service of God. And that is sanctification. In so doing, they, as Paul admonishes in Romans 12:1, pre-sent their bodies a living sacrifice, holy, well-pleasing to God.